Slow waves and tunneling waves can meet at the cutoff wavelengths and/or the transmission band edges of optical and quantum mechanical waveguides. The experimental investigation of this phenomenon, previously performed using various optical microstructures, is challenged by fabrication imperfections and material losses. Here, we demonstrate this phenomenon in situ for whispering gallery modes slowly propagating along a standard optical fiber, which possesses a record uniformity and exceptionally small transmission losses. The slow axial propagation dramatically increases the longitudinal wavelength of light and allows us to measure nanosecond-long tunneling times along tunable potential barriers having the width of hundreds of micrometers. This demonstration paves a simple and versatile way to investigate and employ the interplaying slow and tunneling light.
Bibliographical noteThis paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: https://doi.org/10.1364/OL.384514. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
Funding: Engineering and Physical Sciences Research Council (EPSRC) (EP/P006183/1); Horizon 2020 MCSA COFUND MULTIPLY (H2020 GA 713694).